TRANSFER DEVICE AND IMAGE FORMING APPARATUS
A transfer device includes a plurality of pressing members capable of pressing an image carrier, a contact position changing section that changes a contact position between the image carrier and a transfer roller in a rotational direction of the image carrier in accordance with a type of a recording medium on which an image is formed, and a contact pressure changing section that changes a contact pressure between the image carrier and the transfer roller by changing the number of the pressing member that presses the image carrier according to the contact position.
The entire disclosure of Japanese Patent Application No. 2019-175496 filed on Sep. 26, 2019 is incorporated herein by reference in its entirety.
BACKGROUND Technological FieldThe present invention relates to a transfer device and an image forming apparatus.
Description of Related ArtConventionally, image forming apparatuses having an intermediate transfer system are commonly used. The intermediate transfer system primarily transfers a toner image formed on a photoconductor (an image carrier) to an intermediate transfer belt (an image carrier and an intermediate transfer member) and secondarily transfers the toner image on the intermediate transfer belt to a sheet.
O O O 1 Such an image forming apparatus has a risk of making image defects due to discharge between the photoconductor and a primary transfer roller that are placed facing each other through the intermediate transfer belt. Examples of image defects are white spots and wavy color unevenness (ripples). White spots occur when toner loses electric charge due to discharge and fails to be transferred. Ripples occur when the polarity of electric charges of toner is reversed due to discharge and the toner is collected at downstream of a primary transfer section.
In order to prevent such image defects, the primary transfer roller is usually placed on a downstream side in a moving direction of the intermediate transfer belt so as to be shifted from the photoconductor in the image forming apparatus. In such an arrangement, primary transfer roller 422 presses intermediate transfer belt 421 by a predetermined pressing force, as illustrated in
In recent years, incidentally, there has been a demand for such an image forming apparatus to form images on a sheet having ruggedness formed on its surface such as embossed paper and rough paper (rugged paper). However, it is known that rugged paper is difficult for toner to reach recessed parts during secondary transfer and a secondary transfer performance is deteriorated compared with that for normal paper.
In view of this, a technique for improving the secondary transfer performance for the recessed parts on rugged paper has been proposed. The technique includes weakening the pressing force of the primary transfer roller against the intermediate transfer belt from usual at the time of forming an image on rugged paper. This makes toner on the intermediate transfer belt easier to peel off from the belt, and improves the secondary transfer performance accordingly (see, for example, Japanese Patent Application Laid-Open No. 2010-139955).
There arises a problem, however, that the primary transfer performance is remarkably degraded in the above-mentioned arrangement in which the primary transfer roller is placed on the downstream side in the moving direction of the intermediate transfer belt so as to be shifted from the photoconductor. The problem is caused by failing to form primary transfer nip section N1 when the pressing force of the primary transfer roller is weakened and thus primary transfer roller 422 is pushed back by the tension of intermediate transfer belt 421 as illustrated in
An object of the present invention is to provide a transfer device and an image forming apparatus capable of maintaining a favorable transfer performance regardless of a type of a sheet in an image forming apparatus having an intermediate transfer system.
To achieve at least one of the above-mentioned objects, according to an aspect of the present invention, a transfer device reflecting one aspect of the present invention is a device, including:
a plurality of pressing members capable of pressing an image carrier;
a contact position changing section that changes a contact position between the image carrier and a transfer roller in a rotational direction of the image carrier according to a type of a recording medium on which an image is formed; and
a contact pressure changing section that changes a contact pressure between the image carrier and the transfer roller by changing the number of the pressing member that presses the image carrier according to the contact position.
To achieve at least one of the above-mentioned objects, according to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention is an apparatus including the transfer device.
The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:
Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.
Image forming apparatus 1 is a color image forming apparatus having an intermediate transfer system with electrophotographic process technology. That is, image forming apparatus 1 primarily transfers toner images of yellow (Y), magenta (M), cyan (C), and black (K) formed on photoconductor drums 413 to intermediate transfer belt 421, and superimposes the toner images of the four colors on one another on intermediate transfer belt 421. Then, image forming apparatus 1 secondarily transfers the resultant image to a sheet, thereby forming a toner image.
A longitudinal tandem system is adopted for image forming apparatus 1. In the longitudinal tandem system, respective photoconductor drums 413 corresponding to the four colors of YMCK are placed in series in the travelling direction (vertical direction) of intermediate transfer belt 421, and the toner images of the four colors are sequentially transferred to intermediate transfer belt 421 in one cycle.
As illustrated in
Control section 100 includes central processing unit (CPU) 101, read only memory (ROM) 102, random access memory (RAM) 103 and the like. CPU 101 reads a program suited to processing contents out of ROM 102, develops the program in RAM 103, and integrally controls an operation of each block of image forming apparatus 1 in cooperation with the developed program. At this time, CPU 101 refers to various kinds of data stored in storage section 72. Storage section 72 is composed of, for example, a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.
Control section 100 transmits and receives various data to and from an external apparatus (for example, a personal computer) connected to a communication network such as a local area network (LAN) or a wide area network (WAN), through communication section 71. Control section 100 receives, for example, image data transmitted from the external apparatus, and performs control to form a toner image on sheet on the basis of the image data (input image data). Communication section 71 is composed of, for example, a communication control card such as a LAN card.
Image reading section 10 includes auto document feeder (ADF) 11, document image scanning device 12 (a scanner), and the like.
Auto document feeder 11 causes a conveyance mechanism to feed document D placed on a document tray, and sends out document D to document image scanner 12. Auto document feeder 11 can successively read images (even both sides thereof) of a large number of documents D placed on the document tray at once.
Document image scanner 12 optically scans a document fed from auto document feeder 11 to its contact glass or a document placed on its contact glass, and brings light reflected from the document into an image on the light receiving surface of charge coupled device (CCD) sensor 12a, to thereby read the document image. Image reading section 10 generates input image data on the basis of a reading result provided by document image scanner 12. Image processing section 30 performs predetermined image processing on the input image data.
Operation display section 20 includes, for example, a liquid crystal display (LCD) with a touch panel, and functions as display section 21 and operation section 22. Display section 21 displays various operation screens, image conditions, operating statuses of functions, and the like in accordance with display control signals received from control section 100. Operation section 22 includes various operation keys such as numeric keys and a start key, receives various input operations performed by a user, and outputs operation signals to control section 100.
Image processing section 30 includes a circuit that performs a digital image process suited to initial settings or user settings on the input image data, and the like. For example, image processing section 30 performs tone correction on the basis of tone correction data (tone correction table LUT) stored in storage section 72, under the control of control section 100. In addition to the tone correction, image processing section 30 also performs various correction processes such as color correction and shading correction as well as a compression process, on the input image data. Image forming section 40 is controlled on the basis of the image data that has been subjected to these processes.
Image forming section 40 includes image forming units 41Y, 41M, 41C, and 41K that form images of colored toners of a Y component, an M component, a C component, and a K component on the basis of the input image data, intermediate transfer unit 42, and the like.
Image forming units 41Y, 41M, 41C, and 41K for the Y component, the M component, the C component, and the K component have similar configurations. For ease of illustration and description, common elements are denoted by the same reference signs. Only when elements need to be discriminated from one another, Y, M, C, or K is added to their reference signs. In
Image forming unit 41 includes exposing device 411, developing device 412, photoconductor drum 413, charging device 414, drum cleaning device 415 and the like.
Photoconductor drum 413 is a negatively charged organic photoconductor (OPC) sequentially laminating an undercoat layer (UCL), a charge generation layer (CGL), and a charge transport layer (CTL) on the peripheral surface of a conductive cylinder (an aluminum tube) made of aluminum, for example. The charge generation layer is composed of an organic semiconductor in which a charge generating material (e.g., a phthalocyanine pigment) is dispersed in a resin binder (e.g., polycarbonate), and generates a pair of positive charges and negative charges by light exposure from exposing device 411. The charge transport layer is composed of a hole transport material (an electron-donating nitrogen-containing compound) dispersed in a resin binder (e.g., a polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer.
Control section 100 controls a driving current supplied to a driving motor (not shown in the drawings) that rotates photoconductor drums 413, whereby photoconductor drums 413 are rotated at a constant circumferential speed (linear speed).
Charging device 414 evenly and negatively charges the surface of photoconductor drum 413 having photoconductivity. Exposing device 411 is composed of, for example, a semiconductor laser, and irradiates photoconductor drum 413 with laser light in accordance with an image of each color component. The surface charges (negative charges) of photoconductor drum 413 are neutralized by the positive charges generated in the charge generation layer of photoconductor drum 413 and transported to the surface of the charge transport layer. An electrostatic latent image of each color component is formed on the surface of photoconductor drum 413 by the potential difference from the surroundings.
Developing device 412 is, for example, a developing device of a two-component reverse type, and attaches toners of respective color components to the surface of photoconductor drums 413, and visualizes the electrostatic latent image to form a toner image.
Drum cleaning device 415 includes a drum cleaning blade (hereinafter, simply referred to as a cleaning blade) 416 and the like as a cleaning member sliding on the surface of photoconductor drums 413. Drum cleaning device 415 removes transfer residual toner that remains on the surface of photoconductor drums 413 with cleaning blade 416 after primary transfer.
Intermediate transfer unit 42 includes intermediate transfer belt 421 as an image carrier, primary transfer rollers 422, a plurality of support rollers 423, secondary transfer roller 424, belt cleaning device 426, and the like.
Intermediate transfer belt 421 is composed of an endless belt, and is stretched around the plurality of support rollers 423 in a loop form. At least one of the plurality of support rollers 423 is composed of a driving roller, and the others are each composed of a driven roller. Preferably, for example, roller 423A placed on the downstream side in the belt travelling direction relative to primary transfer rollers 422 for K-component is a driving roller. With this configuration, the travelling speed of the belt at a primary transfer section can be easily maintained at a constant speed. When driving roller 423A rotates, intermediate transfer belt 421 travels in arrow A direction at a constant speed.
Primary transfer rollers 422 are placed on the inner periphery side of intermediate transfer belt 421 to face photoconductor drums 413 of respective color components. Primary transfer rollers 422 are brought into pressure contact with photoconductor drums 413 with intermediate transfer belt 421 therebetween, whereby a primary transfer nip for transferring a toner image from photoconductor drums 413 to intermediate transfer belt 421 is formed.
Secondary transfer roller 424 is placed at a position on the outer peripheral surface side of intermediate transfer belt 421 so as to face backup roller 423B placed on the downstream side in the belt travelling direction relative to driving roller 423A. Secondary transfer roller 424 is brought into pressure contact with backup roller 423B with intermediate transfer belt 421 therebetween, whereby a secondary transfer nip for transferring a toner image from intermediate transfer belt 421 to sheet S is formed.
When intermediate transfer belt 421 passes through the primary transfer nip, the toner images on photoconductor drums 413 are primarily transferred to intermediate transfer belt 421 sequentially. To be more specific, a primary transfer bias is applied to primary transfer rollers 422, and an electric charge of the polarity opposite to the polarity of the toner is applied to the rear side of intermediate transfer belt 421 (the side that makes contact with primary transfer rollers 422) whereby the toner image is electrostatically transferred to intermediate transfer belt 421.
Thereafter, when the sheet passes through the secondary transfer nip, the toner image on intermediate transfer belt 421 is secondarily transferred to the sheet. To be more specific, a secondary transfer bias is applied to secondary transfer roller 424, and an electric charge of the polarity opposite to the polarity of the toner is applied to the rear surface side of the sheet (the side that makes contact with secondary transfer roller 424) whereby the toner image is electrostatically transferred to the sheet, and the sheet is conveyed toward fixing section 60.
Belt cleaning device 426 has a belt cleaning blade and the like which is brought into sliding contact with the surface of the intermediate transfer belt 421, and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer. A configuration (so-called a belt-type secondary transfer unit) in which a secondary transfer belt is installed in a stretched state in a loop form around a plurality of support rollers including a secondary transfer roller may also be adopted in place of secondary transfer roller 424.
Fixing section 60 includes upper fixing section 60A having fixing side members placed on a fixing surface side (a side of the surface on which a toner image is formed) of the sheet, lower fixing section 60B having a back side supporting member placed on the rear surface side (a side of the surface opposite to the fixing surface) of the sheet, heating source 60C, and the like. The back side supporting member is brought into pressure contact with the fixing side members, whereby a fixing nip for conveying the sheet in a tightly sandwiching manner is formed.
Upper fixing section 60A includes endless fixing belt 61, heating roller 62, and upper pressure roller 63, all of which are fixing side members (a belt heating system). Fixing belt 61 is stretched around heating roller 62 and upper pressure roller 63 with a predetermined belt tension (e.g., 400 N).
Heating roller 62 is configured to heat fixing belt 61. Heating roller 62 includes heating source 60C that heats fixing belt 61. Heating roller 62 is, for example, a halogen heater having a configuration that outer peripheral surface of a cylindrical core metal formed of aluminum or the like is coated with a resin layer of PTFE.
Lower fixing section 60B includes, for example, lower pressure roller 64, which is a back side supporting member (a roller pressurization system). Lower pressure roller 64 is formed by coating an outer peripheral surface of a base material layer formed of polyimide (PI) with heat-resistant silicone rubber as an elastic layer, and further coating the outer peripheral surface of the elastic layer with a resin layer of a PFA tube as a surface release layer.
At the fixing nip, fixing section 60 applies heat and pressure to the sheet on which a toner image has been secondarily transferred to fix the toner image on the sheet. Fixing section 60 is placed as a unit in fixing part F. In addition, fixing part F is provided with an air-separating unit that blows air to separate sheet S from the fixing side member.
Sheet conveyance section 50 includes sheet feeding section 51, sheet ejection section 52, conveyance path section 53 and the like. Three sheet feed tray units 51a to 51c included in sheet feeding section 51 store sheets S (standard sheets, special sheets) discriminated on the basis of the basis weight (rigidity), the size, and the like, for each type set in advance. Conveyance path section 53 includes a plurality of conveyance rollers such as a pair of registration rollers 53a, and a double-side conveyance path, and the like.
Sheets S stored in sheet tray units 51a to 51c are output one by one from the uppermost, and conveyed to image forming section 40 by conveyance path section 53. At this time, the registration roller section in which the pair of registration rollers 53a are arranged corrects skew of sheet S fed thereto, and the conveyance timing is adjusted. Then, in image forming section 40, the toner image on intermediate transfer belt 421 is secondarily transferred to one side of sheet S at one time, and a fixing process is performed in fixing section 60. Sheet S on which an image has been formed is ejected out of the image forming apparatus by sheet ejection section 52 including sheet ejection rollers 52a.
Incidentally, there is a demand for image forming apparatus 1 having such an intermediate transfer system to form images on paper having ruggedness formed on its surface (embossed paper, rough paper, and the like, hereinafter collectively referred to as “rugged paper”) as sheet S. In many cases, however, rugged paper is difficult for toner to reach recessed parts during the secondary transfer and the secondary transfer performance is deteriorated compared with the transfer performance for normal paper.
In view of this, a technique for improving the secondary transfer performance for the recessed parts on rugged paper has been proposed. The technique includes weakening the pressing force of primary transfer rollers 422 against intermediate transfer belt 421 from usual at the time of forming an image on rugged paper. This makes toner on intermediate transfer belt 421 easier to peel off from intermediate transfer belt 421, and improves the secondary transfer performance accordingly.
Here,
Further, black arrows in
The setting of primary transfer nip sections N1 as illustrated in
In order to solve such a problem, it is conceivable to weaken the pressing force (the contact pressure) of primary transfer rollers 422 against intermediate transfer belt 421 from usual as illustrated in
Weakening the pressing force of primary transfer rollers 422 in this manner, however, causes primary transfer rollers 422 to be pushed back by the tension of intermediate transfer belt 421 in the arrangement in which primary transfer rollers 422 placed on the downstream side in the moving direction of intermediate transfer belt 421 so as to be shifted from respective photoconductor drums 413, and thus, no primary transfer nip section N1 is formed as illustrated in
To solve this problem, the position of each primary transfer roller 422 needs to be lifted, as illustrated in
Thus, the inventors have found from experiments that the setting of primary transfer nip sections N1 as illustrated in
Therefore, intermediate transfer unit 42 in the present embodiment is provided with a moving mechanism for each primary transfer roller 422 to reciprocate between a first nip position (a normal position or an initial position) illustrated in
In accordance with the present invention, the moving mechanism and control section 100 correspond to “contact position changing section” that changes a contact position between image carriers (intermediate transfer belt 421 and photoconductor drums 413) and primary transfer rollers 422 in a rotational directions of intermediate transfer belt 421 (the image carrier) according to a type of sheet S (a recording medium) on which images are formed.
Hereinafter, an outline and a specific configuration of the moving mechanism (the contact position changing section) in intermediate transfer unit 42 of the present embodiment will be described in detail.
In the present embodiment, four primary transfer rollers 422 facing respective photoconductor drums 413 of YMCK are configured to (collectively) move at a time. To achieve this configuration, shafts of primary transfer rollers 422 are held by a group of members (a pair of side plates in the following examples) and the side plates are configured to be movable with respect to intermediate transfer unit 42. Hereinafter, the side plates are referred to as “movable side plates” for convenience of explanation.
Furthermore, since colored toners of YMC are not used for monochrome printing (monochrome printing of K toner in this example), three primary transfer rollers 422 facing respective photoconductor drums 413 of Y, M, and C configured to be retractable at the time of monochrome printing.
In view of the above, the present embodiment has the following configuration.
A plurality of support rollers 423 (see
In the meantime, each primary transfer roller 422 (see
Thus, the above-described configuration provides a foundation of the moving mechanism (the contact position changing section) that reciprocates primary transfer rollers 422 between the first nip position (the normal position or the initial position) illustrated in
Next, further details of the moving mechanism (the contact position changing section) will be described with reference to
Referring to
Among them, fixed side plates 400 and 400 are placed approximately in parallel to each other at a distance slightly wider than the length of the width direction of intermediate transfer belt 421. Then, a plurality of long connecting members 460 is provided in parallel with primary transfer rollers 422 and the like at the inner surface of fixed side plates 400 and 400, as illustrated in
Fixed side plates 400 and 400 are detachably fixed to the main body of image forming apparatus 1, and have roles of rotatably holding intermediate transfer belt 421, slidably holding movable side plates 430, and the like. That is, as described above, fixed side plates 400 rotatably shaft-support a plurality of support rollers 423, which rotatably support intermediate transfer belt 421 (see
Meanwhile, movable side plates 430 rotatably hold four primary transfer rollers 422 respectively facing to photoconductor drums 413 that carry toner images of respective four colors (i.e., Y, M, C, and K).
In the present embodiment, the outer surfaces of movable side plates 430 respectively contact with the inner surfaces of the pair of fixed side plates 400, and the position of movable side plates 430 relative to fixed side plates 400 is changed, i.e., movable side plates 430 slide and move. This enables to adjust the positions of primary transfer rollers 422 relative to photoconductor drums 413 and the like.
Further, in the present embodiment, intermediate transfer unit 42 has movable side plates 430 (U) and movable side plates 430 (K) separately. Movable side plates 430 (U) rotatably hold primary transfer rollers 422 (Y), 422 (M), and 422 (C), which form primary transfer nip sections N1 for respective images of YMC (three colors). Movable side plates 430 (K) rotatably hold primary transfer roller 422 (K), which forms primary transfer nip section N1 for an image of K (black).
That is, in the present embodiment, primary transfer rollers 422 (Y), 422 (M), and 422 (C) move integrally with a moving operation of movable side plates 430 (U), and primary transfer roller 422 (K) moves with a moving operation of movable side plates 430 (K).
In relation to the present invention, movable side plates 430 (K) correspond to “first movable side plates” that hold a shaft of transfer roller 422 (K) transferring black images, and movable side plates 430 (U) correspond to “second movable side plates” that hold shafts of transfer rollers 422 (Y) to (M) transferring images of respective colors other than black.
Such a configuration mainly intends to move movable side plates 430 (U) to retract (release the contact pressure from) primary transfer rollers 422 respectively facing photoconductor drums 413 of Y, M, and C at the time of monochrome printing. The detail of the configuration will be described later.
As illustrated in
Out of these two, the upper motor 80 is a driving source for moving a pair of the movable side plates 430 (U) in the vertical direction. The pair of movable side plates 430 (U) holds primary transfer rollers 422 (Y), 422 (M), and 422 (C) primarily transferring toner images of respective colors (Y, M, or C), which are respectively carried by three photoconductor drums 413 from the top of the apparatus, onto intermediate transfer belt 421.
The lower motor 81, on the other hand, is a driving source for moving a pair of the movable side plates 430 (K) in the vertical direction. The pair of movable side plates 430 (K) holds primary transfer roller 422 (K) primarily transferring a toner image of K (black), which is carried by the lowest photoconductor drum 413 in the apparatus, onto intermediate transfer belt 421.
Here,
As illustrated in
Thus, in the present embodiment, motor 80 is rotated in a predetermined direction under the control of control section 100, the driving force is transmitted to cam shaft 401 through a plurality of gears (see
Further, referring to the state illustrated in
Incidentally, since the same mechanism described above is applied for moving the lower movable side plates 430 (K) in the vertical direction by the driving of motor 81 (see
In the present embodiment as described above, motors 80 and 81 rotate under the control of control section 100, and thereby movable side plates 430 (U) and 430 (K) move in the vertical direction relative to fixed side plates 400.
The vertical movement makes it possible to adjust the position of primary transfer nip section N1 between each primary transfer roller 422 held by movable side plates 430 and a corresponding photoconductor drum 413 via intermediate transfer belt 421. That is, when movable side plates 430 (U) and 430 (K) move upward, nip positions also move upward, which is an upstream side of a conveying direction (see
Further, in order to adjust the pressing force (nip pressure or contact pressure) of primary transfer rollers 422 with respect to photoconductor drums 413, the nip pressure needs to be switched with the vertical movement of movable side plate 430 by a certain means. That is, it is preferable to have a mechanism that switches the nip pressure (contact pressure) to be strong at the nip positions for normal paper illustrated in
Furthermore, the nip positions for normal paper illustrated in
Therefore, it is insufficient in the present embodiment for movable side plates 430 to simply rotatably support primary transfer rollers 422, and it is preferable to provide a mechanism to movably hold primary transfer rollers 422 in a direction toward or away from photoconductor drums 413 (the lateral direction in
Considering these many technical problems, intermediate transfer unit 42 in the present embodiment has a plurality of springs (two springs in the following example, one of which is strong and the other is weak) and a mechanism for switching the number of springs that press primary transfer rollers 422 and accordingly image carriers (intermediate transfer belt 421 or the like) along with the vertical movement of movable side plates 430, i.e., springs used as a source of contact pressure of the nip. In accordance with the present invention, such a mechanism corresponds to “contact pressure changing section” that changes the contact pressure between image carriers and the transfer rollers 422. Details will be described below.
Although only one end of primary transfer roller 422 is illustrated in these drawings, the configuration in
Note that intermediate transfer belt 421 and photoconductor drum 413 as image carriers are located on the right side in
As illustrated in
To be more specific, inside bearing 444 and outside bearing 443 hold the shaft of primary transfer roller 422 from above and below as illustrated in
In addition, spring 442 for pressing (energizing) inside bearing 444 is placed between base member 435 and inside bearing 444. Likewise, spring 441 for pressing (energizing) outside bearing 443 is placed between base member 435 and outside bearing 443.
In accordance with the present invention, spring 442 for pressing inside bearing 444 corresponds to “first pressing member”, and spring 441 for pressing outside bearing 443 corresponds to “second pressing member”.
That is, two springs 441 and 442 are provided in the present embodiment, and energize (press) primary transfer roller 422 (the shaft thereof) in the direction of intermediate transfer belt 421 and photoconductor drum 413 illustrated in
In the present embodiment, spring 442, which is an inner spring of the two springs (upper in
On the other hand, spring 441, which is an outer spring of the two springs (lower side in
To be more specific, spring 441 constantly energizes (presses) outside bearing 443 to the right direction in
Therefore, in the state illustrated in
Further, in the state illustrated in
At this time, a strong contact pressure (nip pressure) is applied to primary transfer nip sections N1 as illustrated in
In the state of primary transfer nip sections N1 illustrated in
In contrast, inside bearing 444 and spring 442 move upward with primary transfer roller 422 when movable side plate 430 moves upward from the state illustrated in
Incidentally, as illustrated in
Arm section 450 described above is then provided on the inner surface of fixed side plate 400 corresponding to the area of groove section 430a. Such arm section 450 is fixed to the inner surface of fixed side plate 400 by a screw or the like, and is placed so that tip 450a of arm section 450 extends downward through groove section 430a of movable side plate 430.
Further, as referred to
According to this configuration, when movable side plate 430 moves upward from the state illustrated in
At this time, the contact (the engagement, in other words) between protruding surface 443a of outside bearing 443 and end surface 444a (upper side) of inside bearing 444, described above with reference to
That is, when movable side plate 430 is lifted from the position illustrated in
Thus, when movable side plate 430 moves upward from the state illustrated in
Primary transfer nip sections N1 at this time have a weaker nip pressure (contact pressure) than the normal state as illustrated in
As described above, the moving operation of movable side plate 430 upward from the initial state illustrated in
To summarize, when movable side plates 430 and primary transfer nip sections N1 are located at the lower positions (the downstream side of the conveying direction), which is the normal state illustrated in
Thus, the present embodiment provides a mechanism for mechanically switching the strength of the nip pressure (contact pressure) according to the vertical movement of movable side plates 430. The mechanism yields a simple, space-saving configuration and an appropriate switching according to the type of sheet S to be used.
That is, in the present embodiment, control section 100 controls the driving of motors 80 and 81 so as to switch between the positions of the above-mentioned primary transfer nips according to the type of sheet S to be used (sheet information such as a sheet setting profile) when a print job is executed.
To be more specific, when the type of sheet S to be used is rugged paper such as embossed paper, control section 100 appropriately controls the driving of motors 80 and 81 so as to set movable side plates 430 and primary transfer rollers 422 to the upper positions, which is the state described in
In contrast, when the type of sheet S to be used is other than rugged paper, control section 100 appropriately controls the driving of motors 80 and 81 so as to set movable side plates 430 and primary transfer rollers 422 to the lower positions, which is the state described in
Further, control section 100 drives and controls motor 80 so as to retract the above-described movable side plates 430 (U) and accordingly primary transfer rollers 422 (Y), 422 (Y), and 422 (C) to retracted positions when a monochrome print job is executed with K toner only.
To be more specific, control section 100 rotatably drives motor 80 so as to lower movable side plates 430 (U) from the initial state illustrated in
In the present embodiment, such a simple control enables to retract movable side plates 430 (U) and the like to the retracted positions, and to release primary transfer nip sections N1 between primary transfer rollers 422 (Y), 422 (Y), and 422 (C) and corresponding photoconductor drums 413.
Hereinafter, a mechanism for achieving such a retracting operation will be described in detail. Note that such a mechanism corresponds to an additional function of the contact position changing section described above.
Referring to
Such a configuration of groove section 430a allows movable side plate 430 to move in the direction to retract from photoconductor drum 413 (a rear side in
Further, as illustrated in
In such a structure, the above-described inclined sides of guide grooves 430b of movable side plates 430 abut against the upper side of respective connecting members 460 when movable side plates 430 are lowered from the initial state illustrated in
This operation allows movable side plates 430 (430 (U)) as well as primary transfer rollers 422 (Y), 422 (M), and 422 (C) to be retracted from image carriers (intermediate transfer belt 421 and corresponding photoconductor drums 413).
In the present embodiment, the above-described configuration and the retracting operation thus make it possible to release primary transfer nip sections N1 between primary transfer rollers 422 (Y) to (C) and corresponding photoconductor drums 413 via intermediate transfer belt 421 at the time of monochrome printing.
In addition, the retracting operation enables to secure and/or improve a durability of primary transfer rollers 422 (Y) to (C), which are not used for monochrome printing, and intermediate transfer belt 421.
(Configuration for Improving Maintainability)
Hereinafter, a configuration for mainly improving workability and convenience of an operator at the time of maintenance of intermediate transfer unit 42, in other words, a more detailed configuration of the above-described “contact pressure changing section” will be described.
As an additional configuration of the contact pressure changing section described above, base member 435 includes arm 436 protruding in a rod shape from a position facing the rotary shaft of primary transfer roller 422 as illustrated in
In addition, locking section 444b protruding in a wedge shape toward arm 436 is provided at a portion of inside bearing 444 facing arm 436 as illustrated in
In the present embodiment having such a configuration (first regulating member), locking sections 436a and 444b engage with each other when primary transfer nip sections N1 are released and various components such as inside bearing 444 are moved to the right side in
This operation makes it possible to prevent defects such as the coming-off of bearings (444 and 443), springs (442 and 441) and the like as described above when primary transfer nip sections N1 are released by retracting movable side plates 430 and the like from intermediate transfer belt 421.
In addition, when primary transfer nips N1 are released, for example, by removing intermediate transfer belt 421 or intermediate transfer unit 42 as a whole, bearings (444 and 443), springs (442 and 441), and the like can be effectively prevented from defects such as scattering. Therefore, in the present embodiment, it is possible to improve the workability and the convenience of the operator at the time of maintenance of intermediate transfer unit 42 or the like.
Further, as an additional configuration of the contact pressure changing section described above, tip 450a of arm section 450 and inclined section 443b of outside bearing 443 face each other as described above with reference to
In accordance with the present invention, arm section 450 of fixed side plate 400 (the tip 450a side in particular) and inclined section 443b of outside bearing 443 correspond to “second regulating member” that regulates or prevents spring 441 and the like from coming off.
That is, according to the above configuration, when primary transfer nips N1 are released, for example, by removing intermediate transfer belt 421 or intermediate transfer unit 42 as a whole from the initial state illustrated in
As described above in detail, intermediate transfer unit 42 in image forming apparatus 1 of the present embodiment includes the contact position changing section that changes contact positions (nip positions) between the image carriers, namely intermediate transfer belt 421 and photoconductor drums 413, and primary transfer rollers 422 in the rotational direction of intermediate transfer belt 421 (the image carrier) according to the type of sheet S (the recording medium) on which an image is formed, and the contact pressure changing section that changes the primary transfer nip pressure (the contact pressure) by changing the number of pressing members (springs 441 and 442) that press photoconductor drums 413 and the like according to the contact position.
Intermediate transfer unit 42 of the present embodiment having such a configuration makes it possible to change positions of primary transfer nips N1 and the pressing force via intermediate transfer belt 421 at a time in accordance with the type of sheet S to be printed or the like. Therefore, in the present embodiment, the transfer performances, that is, the primary transfer performance to intermediate transfer belt 421, and the secondary transfer performance to sheet S can be maintained in good condition regardless of the type of sheet S.
To be more specific, intermediate transfer unit 42 makes the primary transfer nip pressure (contact pressure) lower than usual by reducing the number of springs (441 and 442), which press the shaft of primary transfer rollers 422, when movable side plates 430 holding the shafts of primary transfer rollers 422 move (are lifted) from the initial position (see
With such a configuration, it is possible to maintain the transfer performance of an image to rugged paper in good condition even at the time of forming an image on the rugged paper, which generally is apt to have a lower transfer performance.
Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purpose of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.
Claims
1. A transfer device, comprising:
- a plurality of pressers capable of pressing an image carrier;
- a contact position changer that changes a contact position between the image carrier and a transfer roller in a rotational direction of the image carrier according to a type of recording medium on which an image is formed; and
- a contact pressure changer that changes a contact pressure between the image carrier and the transfer roller by changing a number of the plurality of pressers that press the image carrier in accordance with the contact position.
2. The transfer device according to claim 1, wherein
- the plurality of pressers comprise a first presser and a second presser, wherein
- the first presser presses the image carrier when the type of recording medium is rugged paper, and both the first presser and the second presser press the image carrier when the type of the recording medium is other than rugged paper in the contact pressure changer.
3. The transfer device according to claim 1, wherein the contact position changer comprises movable side plates which hold a shaft of the transfer roller and face both sides of the image carrier in a shaft direction.
4. The transfer device according to claim 3, wherein the contact position changer changes a position of the transfer roller by moving the movable side plates in accordance with a rotation angle of a cam.
5. The transfer device according to claim 4, wherein the contact position changer separates the movable side plates from the image carrier in accordance with the movement of the movable side plates.
6. The transfer device according to claim 2, wherein the contact pressure changer comprises a first regulator that regulates coming-off of the first presser.
7. The transfer device according to claim 2, wherein the contact pressure changer comprises a second regulator that regulates coming-off of the second presser.
8. The transfer device according to claim 3, wherein:
- the contact pressure changer comprises a second regulator that regulates coming-off of the second presser; and
- the second regulator releases the pressing against the image carrier by the second presser in accordance with a movement of the movable side plates.
9. The transfer device according to claim 5, wherein:
- the movable side plates comprise first movable side plates that hold the shaft of the transfer roller transferring a black image, and second movable side plates that hold the shafts of the transfer rollers transferring an image of colors other than black; and
- the contact position changer separates the second movable side plates from the image carrier at the time of monochrome printing.
10. An image forming apparatus, comprising the transfer device according to claim 1.
Type: Application
Filed: Sep 3, 2020
Publication Date: Apr 1, 2021
Inventor: Taro TAKECHI (Saitama)
Application Number: 17/011,706